The invention relates to gas turbine engines. More particularly, the invention relates to gas turbine engines having center-tie rotor stacks.
A gas turbine engine typically includes one or more rotor stacks associated with one or more sections of the engine. A rotor stack may include several longitudinally spaced apart blade-carrying disks of successive stages of the section. A stator structure may include circumferential stages of vanes longitudinally interspersed with the rotor disks. The rotor disks are secured to each other against relative rotation and the rotor stack is secured against rotation relative to other components on its common spool (e.g., the low and high speed/pressure spools of the engine).
Numerous systems have been used to tie rotor disks together. In an exemplary center-tie system, the disks are held longitudinally spaced from each other by sleeve-like spacers. The spacers may be unitarily-formed with one or both adjacent disks. However, some spacers are often separate from at least one of the adjacent pair of disks and may engage that disk via an interference fit and/or a keying arrangement. The interference fit or keying arrangement may require the maintenance of a longitudinal compressive force across the disk stack so as to maintain the engagement. The compressive force may be obtained by securing opposite ends of the stack to a central shaft passing within the stack. The stack may be mounted to the shaft with a longitudinal precompression force so that a tensile force of equal magnitude is transmitted through the portion of the shaft within the stack.
Alternate configurations involve the use of an array of circumferentially-spaced tie rods extending through web portions of the rotor disks to tie the disks together. In such systems, the associated spool may lack a shaft portion passing within the rotor. Rather, separate shaft segments may extend longitudinally outward from one or both ends of the rotor stack.
Desired improvements in efficiency and output have greatly driven developments in turbine engine configurations. Efficiency may include both performance efficiency and manufacturing efficiency.
U.S. patent application Ser. No. 10/825,255, Ser. No. 10/825,256, and Ser. No. 10/985,863 of Suciu and Norris (hereafter collectively the Suciu et al. applications, the disclosures of which are incorporated by reference herein as if set forth at length) disclose engines having one or more outwardly concave inter-disk spacers. With the rotor rotating, a centrifugal action may maintain longitudinal rotor compression and engagement between a spacer and at least one of the adjacent disks. This engagement may transmit longitudinal torque between the disks in addition to the compression.